28 research outputs found
A new family of non--linear filters for background subtraction of wide--field surveys
In this paper the definitions and the properties of a newle dedicated set of
high-frequency filters based on smoothing-and-clipping are briefly described.
New applications for reduction of wide--field 2048x2048 CCD spectral and direct
images of a new deep survey KISS (KPNO International Spectral Survey) are also
presented. The developed software is available both as a C subroutine and as an
installed MIDAS environment command.Comment: 8 pages with 2 Postscript figures. The text with full figures
obtainable from this http URL
http://193.125.89.73/~akn/cont_with_figures.ps.g
The Brera Multi-scale Wavelet (BMW) ROSAT HRI source catalog. II: application to the HRI and first results
The wavelet detection algorithm (WDA) described in the accompanying paper by
Lazzati et al. is made suited for a fast and efficient analysis of images taken
with the High Resolution Imager (HRI) instrument on board the ROSAT satellite.
An extensive testing is carried out on the detection pipeline: HRI fields with
different exposure times are simulated and analysed in the same fashion as the
real data. Positions are recovered with few arcsecond errors, whereas fluxes
are within a factor of two from their input values in more than 90% of the
cases in the deepest images. At variance with the ``sliding-box'' detection
algorithms, the WDA provides also a reliable description of the source
extension, allowing for a complete search of e.g. supernova remnant or cluster
of galaxies in the HRI fields. A completeness analysis on simulated fields
shows that for the deepest exposures considered (~120 ks) a limiting flux of
\~3x10^{-15} erg/cm2/s can be reached over the entire field of view. We test
the algorithm on real HRI fields selected for their crowding and/or presence of
extended or bright sources (e.g. cluster of galaxies and of stars, supernova
remnants). We show that our algorithm compares favorably with other X-ray
detection algorithms such as XIMAGE and EXSAS. A complete catalog will result
from our analysis: it will consist of the Brera Multi-scale Wavelet Bright
Source Catalog (BMW-BSC) with sources detected with a significance >4.5 sigma
and of the Faint Source Catalog (BMW-FSC) with sources at >3.5 sigma. A
conservative estimate based on the extragalactic log(N)-log(S) indicates that
at least 16000 sources will be revealed in the complete analysis of the whole
HRI dataset.Comment: 6 pages, 11 PostScript figures, 1 gif figure, ApJ in pres
AGAPE, an experiment to detect MACHO's in the direction of the Andromeda galaxy
The status of the Agape experiment to detect Machos in the direction of the
andromeda galaxy is presented.Comment: 4 pages, 1 figure in a separate compressed, tarred, uuencoded uufile.
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Temperatures and optical depths of Saturn's rings and a brightness temperature for Titan
The Star Cluster System of the NGC 7673 Starburst
We investigate the star cluster system in the starburst galaxy NGC 7673 using
archival Hubble Space Telescope WFPC2 broad-band images. For the first time we
are able to examine the internal structures of the prominent optical clumps in
this galaxy. The clumps are composed of young stars, 16-33 % of which are in
bright star clusters. We identify 268 star cluster candidates in both the F555W
and F814W images, and 50 clusters with the F255W filter. These data allow us to
estimate ages and masses using color-magnitude and two-color diagrams for our
sample. We find a population of young, < 6 Myr clusters located throughout the
galaxy with concentrations in the clumps. Star cluster mass estimates are 5-50
x 10^4 M_solar for the brightest objects. The starburst remains active in
physically well-separated regions, indicating a widespread starburst trigger.
We discuss clump lifetimes, their implications for the future evolution of NGC
7673, and possible relationships to high redshift starbursts.Comment: 18 pages, 15 figures. Accepted for publication in Astronomy &
Astrophysic
Variable stars towards the bulge of M31: the AGAPE catalogue
We present the AGAPE astrometric and photometric catalogue of 1579 variable
stars in a 14'x10' field centred on M31. This work is the first survey devoted
to variable stars in the bulge of M31. The R magnitudes of the objects and the
B-R colours suggest that our sample is dominated by red long-period variable
stars (LPV), with a possible overlap with Cepheid-like type II stars. Twelve
nova candidates are identified. Correlations with other catalogues suggest that
2 novae could be recurrent novae and provide possible optical counterparts for
2 supersoft X-ray sources candidates observed with Chandra.Comment: 11 pages, Latex, accepted for publication in A&
Clumpy, Irregular Galaxies, Clues of Galaxy Evolution-Spectroscopic Study of KUG1626+413
International audienceno abstrac
AGAPE, an experiment to detect MACHO's in the direction of the Andromeda galaxy
The status of the Agape experiment to detect Machos in the direction of the andromeda galaxy is presented